The invention relates to a fire fighting apparatus comprising a plurality of spray heads, a tube system for leading extinguishing medium from an extinguishing medium source having a volume for extinguishing medium to the spray heads, at least one drive gas source for driving extinguishing medium at a high pressure via the tube system to the spray heads and release means for activating at least one of the spray heads. Such fire fighting apparatuses are known e.g. from the International Patent Application with the publication number WO 92/22353.
Prior art fire fighting apparatuses comprise one container or a number of containers for extinguishing medium, the containers being positioned adjacent to each other and arranged to deliver extinguishing medium via a tube system to spray heads or sprinklers. The length and shape of the tube system depend on the application and the operating principle. Fire fighting apparatuses for bigger spaces, such as hotels, ships and industrial buildings, often have long tube systems.
The source of extinguishing medium of the fire fighting apparatuses in said applications can be e.g. the water mains, or a water container, from which water is pumped to the spray heads. Alternatively, the source of extinguishing medium can be a water bottle, to which is coupled a pressure gas bottle capable of driving the water (or another extinguishing medium) out of the bottle to the spray heads. Such a combination constitutes a hydraulic accumulator.
Long tunnels are technically particularly difficult spaces to extinguish a fire in. The tunnels can have a length of several kilometres—even some ten kilometres—and a diameter of e.g. 3 metres. The tunnels often contain cables. A cable fire may cause great damage. Extinction of a fire in such long tunnels is assumed to be so difficult to arrange that, in most cases, the tunnels do not contain any fire fighting system at all. In case if the length of the tunnel is some kilometres and the intention is to lead extinguishing liquid, such as water, into the tunnel via a tube from one end thereof to a distance of some kilometres from said tunnel end, a drive pressure so high is required that, on account of pressure losses in the tube, it cannot be generated, in practice.